Photographic process



United States Patent 2,844,465 PHOTOGRAPI-IIC PROCESS. Lyman Chalkley,Prince. Georges County, Md.

N0 Drawing. Application March 17,1954 Serial No. 416,965-

Claims. (Cl. 96-48) This invention relates to a photographic process,and more particularly to one in which the image is completely' developedby action of light, and is then fixed by' the evaporation of' a volatilecomponent of the photosensitive material.

An object of the invention is to provide a photographic process whichproduces finished prints without chemical manipulation. The process isextremely simple; It is very flexible in that images may be obtained ina variety of colors on paper, cloth and film. Dimensional stability ofpaper prints is good. Other advantages will appear from the followingdescription. j i The. process employs a photosensitive system comprisingat least two components both of which are necessary for thephotochemical reaction, and one of which is volatile, that is has aboiling point at a pressure of 760 mm. of mercury of less than 325 C.The process consists in printing'out a fully formed image upon asuitably sensitized paper, cloth, or other material, and fixing theimage by evaporation of the volatile component.

Co-pending application Serial No; 194,017, now'Patent Number 2,676,887,issued April 27, 1954, of which the present application is acontinuation-in-part discloses a photosensitive system consisting of'abasic dye cyanide and an organic photoactivator, which may be volatile.Many of the photosensitive materials described in the co-pendingapplication may be usedin the presently described process.

For the present process materials sensitized; with hydrophobic dyecyanides are satisfactory. Examples; of

' suitable hydrophobic dye cyanides are the cyanides of crystal violet,malachite green, rosaniline, pararosaniline, brilliant green, andsimilar dyes. On the other hand, cyanides which contain hydrophilicgroups, such as quaternary ammonium, and sulfonic acid, should not be.employed to sensitize the materials used in the present process. Thuspaper sensitized with the cyanide of methyl green, which would contain aquaternary ammonium group, would not be suitable.

Any photoactivator may be employed if it is sulficiently volatile.Examples of suitable activators are, acetonitrile, valeronitrile,'capronitrile, aniline, monomethylaniline, phenylmethyl carbinol, benzylalcohol, beta-.phenylethyl alcohol, veratrole, ethylene glycol diethylether, tetraethylene glycol dimethyl ether. In addition to activatorsdisclosed in the co-pending application, previously known activators,such as ethyl alcohol and acetic acid, may be used. However, forpractical speed in fixing the image, the relatively non-volatileactivators are less desirable. Thus ethyl and butylphosphates aresatisfactory activators for materials used in the present process, butthe ortho and meta cresyl phosphates, while excellent activators, areless suitable because of their low volatility. The activator used in thepresent process should preferably boil below 325 C. at a pressure of 760mm. of mercury. 1

ICC

Because the activated dye cyanides are sensitive only to ultravioletradiation, printing should be carried out by direct sunlight, anultraviolet cored. carbon arc, a quartz mercury lamp. sunlamp, or, othersource ofv radiations shorter than 3300 A. U. Any printing frame glassthat may be used, and the film, tracing cloth, paper or. other supportfor the master copy, from which the print is made, should transmit someradiation shorter than 3300 A. U. Commercial products suitable forprinting frame glasses are Vitaglass, Corex D, Corex A, Coming glassN'o..7-9 IO, fuzed quartz etc. Ordinary photographic film is quitesuitable for the: master copy support, as are most of the commerciallyavailable tracing cloths.

Printing is carried out until: the image has the desired depth of color.The image. from. a negative master copy is a positive- The, image. isfully formed in printingv and no. operation of chemical development isemployed.

Fixing; is carried. out'in darkness or light free from the ultravioletradiation to. which the materials are sensitive, and. consists inevaporation of the. activator. A, variety of methods maybe employed,such'as:

(1) Hanging-the print at room temperature in free.

Method. 1. is always applicable and requires normallyonly an. hour ortwo with paper prints when the activator has a boiling point of-up to-210 C. Method 2 also is always. applicable and is faster than 1. Methods3 and- 4 are still faster, but the temperatures employed.

should be adapted to the material being fixed. Generallyit is desirableto use temperatures that are not higher than a about C. to avoid heatinduced decompositions.

Even 100 C. may at times be too high a temperature. because, forexample; a film containing a low boiling activator might be blistered bythe vapor formed rapidly and trapped in. the. film.

Fixing is complete when the activator has. been re moved. Adequacy offixing can be determined by a brief test exposure of 'a portion of theprint to ultraviolet radiation. When no color develops on such exposurefixing is adequate. However, removal of the:

activator can: often be judged. by odor or appearance of the print. Ofcourse only volatile activators should be present in the photosensitivematerial. If a non-volatile activator is present as an impurity in thevolatile activator, paper, film, or other materials employed, fixingwill not be complete.

The following examples will illustrate the process more clearly.

Example 1 ing on it a stream of air heated to 100 until the odor of theresorcinol dimethyl ether has disappeared, and an exposure of a portionof the print to direct sunlight for 1 minute produces no appreciableimage.

Example 2 Water leaf paper is sensitized by dipping in a A of 1%solution of pararosaniline cyanide in acetonitrile, and the excesssolution removed by blotting with a fresh 3 piece of paper. Thesensitized paper is printed immediately by sunlight in a frame equippedwith a Vitaglass glass. A silver photographic negative on safety film isused as the master copy. Between the negative and the sensitized paperis placed a film .of thin. clear colorless cellophane to protect thenegative from possible damage by diffusion of the acetonitrile. Behindthe sensitized paper is placed a sheet of thin aluminum foil to preventevaporation of acetonitrile during printing. When the image has beenprinted to suflicient depth, the print is fixed by hanging in free airat room temperature for about ten minutes.

Example 3 Paper sensitized and printed as in Example 2 is fixed byheating to 100 for 1 minute in a constant tempera ture oven.

Example 4 stencil in a printing frame equipped with a Coming 7910 glassand a sheet of aluminum foil behind the paper to prevent evaporation ofthe alcohol. Printing is by the radiation from a quartz mercury lampuntil the green image is suificiently strong. The print is fixed byexposure for 1 minute to a stream of air heated to. 100 C.

Example 5 The images formed on the sensitized water leaf papers tend torun, i. e. to difiuse laterally in the paper, and thus to give a softfocus eifect to the print even when the negative is sharp. For somepurposes this eflfect is desirable, but not for the reproduction of finelines or print. Sharper images are obtained by the use of sized papers.A rosin sized paper is sensitized by brushing with a fresh /2 of 1%solution of crystal violet cyanide in benzyl alcohol. (At lowtemperatures the dye cyanide may crystallize from old solutions of thisconcentration.) Printing is carried out immediately after sensitizationbe hind an India ink drawing on tracing cloth, and the image is fixed byexposure of the print for a few minutes to a stream of air heated to 100C.

Example 6 Starch sized paper is sensitized by brushing with a solutionof crystal violet cyanide saturated at 16 C. in phenylmethyl carbinol.The paper is printed behind a 6!. master copy printed in black ink onWinston Extra Thin tracing paper. The print is fixed by blowing a streamof air on it at room temperature.

I claim:

1. A photographic process comprising the steps of printing out an imageby ultraviolet radiation upon material sensitized with a hydrophobicamino triphenylmethane dye cyanide activated by an organic activatorboiling below 325 C. at a pressure of 760 mm. of mercury selected fromthe group consisting of veratrole, resorcinol dimethyl ether, anethylene glycol ether, a phosphoric acid ester of a monohydroxycompound, an aromatic amine containing a hydrogen atom on the nitrogenatom, a nitrile in which the cyano group is attached to a carbon atomwhich also holds a hydrogen atom, an aromatic carbinol and a loweraliphatic alcohol and fixing the image by blowing a stream of air overthe print until the activator is completely removed.

2. The process of claim 1 in which the air is heated.

3. The process of claim 1 in which the activator boils below C. and isevaporated by blowing a stream of air over the print at a temperatureabove the boiling point of said activator but not in excess of about 100C.

4. A photographic process comprising the steps of printing out an imageby ultraviolet radiation upon material sensitized with a hydrophobicamino triphenylmethane dye cyanide activated by an organic activatorboiling below 325 C. at a pressure of 760 mm. of mercury selected fromthe group consisting of veratrole, resorcinol dimethyl ether, anethylene glycol ether, a phosphoric acid ester of a monohydroxycompound, an aromatic amine containing a hydrogen atom on the nitrogenatom, a nitrile in which the cyano group is attached to a carbon atomwhich also holds a hydrogen atom, an aromatic carbinol, and a loweraliphatic alcohol; and fixing the image by heating the print above theboiling point of said activator until the activator is completelyevaporated.

5. The process of claim 4 in which the activator boils below 100 C. andthe print is heated above the boiling point of said activator but not inexcess of 100 C.'

References Cited in the file of this patent UNITED STATES PATENTS2,308,058 Crowley Ian. 12, 1943 2,324,060 Boughton July 13, 19432,346,090 Staehle Apr. 4, 1944 2,441,561 Chalkley May 18, 1948 2,676,887Chalkley Apr. 27, 1954

1. A PHOTOGRAPHIC PROCESS COMPRISING THE STEPS OF PRINTING OUT AN IMAGEBY ULTRAVIOLET RADIATION UPON MATERIAL SENSITIZED WITH A HYDROPHOBICAMINO TRIPHENYLMETHANE DYE CYANIDE ACTIVATED BY AN ORGANIC ACTIVATORBOILING BELOW 325*C. AT A PRESSURE 760 MM. OF MERCURY SELECTED FROM THEGROUP CONSISTING OF VERATROLE, RESORCINOL DIMETHYL ETHER, AN ETHYLENEGLYCOL ETHER, A PHOSPHORIC ACID ESTER OF A MONOHYDROXY COMPOUND, ANDAROMATIC AMINE CONTAINING A HYDROGEN ATOM ON THE NITROGEN ATOM, ANITRILE IN WHICH THE CYANO GROUP IS ATTACHED TO A CARBON ATOM WHICH ALSOHOLDS A HYDROGEN ATOM, AN AROMATIC CARBINOL AND A LOWER ALIPHATICALCOHOL AND FIXING THE IMAGE BY BLOWING A STREAM OF AIR OVER THE PRINTUNTIL THE ACTIVATOR IS COMPLETELY REMOVED.